全新java初学者实践教程6(Java SE5.0版)
wk'|gI[W 基本语法3
XN'x`%!*3# 0_J<=T?\"s ULkjY1& 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
o!dTB,Molr 3mIVNT@S9 [font="Times] 1.循环语句[font="Times]:while,do-while,for
T&j_7Q\;vI "at*G>+ [font="Times]2.分支语句[font="Times]:if-else,switch,
%nSLe~b [font="Times]
S{XV{o 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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g#2Q1t,~U 4.异常处理语句[font="Times]:try-catch-finally,throw
\,+act"v 0 V}knR.l 实践:
NffZttN [font="Times] 1.循环语句
n3da@ClBt [font="Times] while 语句
MR} GxI [font="Times]class While {
-NGY+1 [font="Times]public static void main(String args[]) {
i?.MD+f8 [font="Times]int n = 10;
h%|Jkx!v-t [font="Times]while(n > 0) {
-U`]/ [font="Times]System.out.println("tick " + n);
>j%HVRW [font="Times]n--;
2WE_NEpJI [font="Times]}
\=P+]9 [font="Times]}
]k-<[Z;I, [font="Times]}
1Y'9|+y+ [font="Times] do…while 语句
(&npr96f [font="Times] class DoWhile {
""|vhgP [font="Times]public static void main(String args[]) {
8vjaQ5
[font="Times]int n = 10;
D~P I_*h. [font="Times]do {
fo;Ftf0 [font="Times]System.out.println("tick " + n);
E Z15 [font="Times]n--;
]2`PS<a2 [font="Times]} while(n > 0);
X~(%Y#6 [font="Times]}
3C=ON.1eg [font="Times]}
~G+o;N,V 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
vN=e1\ [font="Times] for语句
p~vq1D6 [font="Times] class ForTick {
5xtIez]x? [font="Times]public static void main(String args[]) {
Ztu _UlGC [font="Times]int n;
8+5z -vd [font="Times]for(n=10; n>0; n--)
uQIa"u7 [font="Times]System.out.println("tick " + n);
'85@U`e. [font="Times]}
v1*Lf/ [font="Times]}
Lf`LFPKb 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
35|F?Jx.r 还有啊,[font="Times]for循环的部分可以为空的
!$ItBn/_ [font="Times]class ForVar {
}d?"i@[ [font="Times]public static void main(String args[]) {
yhhW4rz [font="Times]int i;
=B-a]?lM [font="Times]boolean done = false;
yqi=9NB [font="Times]i = 0;
~<!b}Hv [font="Times]for( ; !done; ) {
5Arx"=c [font="Times]System.out.println("i is " + i);
\D}K{P [font="Times]if(i == 10) done = true;
)FVW/{NF@q [font="Times]i++;
,Wtod|vx\U [font="Times]}
n%yMf!M
.: [font="Times]}
|E/U(VS3l~ [font="Times]}
循环语句的例子下载 <!g q9 [font="Times] 2.分支语句[font="Times]
WP{!|d& [font="Times] if/else语句
Xk8+ [font="Times]class IfElse {
zX*+J"x [font="Times]public static void main(String args[]) {
MLf,5f;e [font="Times]int month = 4; // April
!|}(tqt [font="Times]String season;
A14} [font="Times]if(month == 12 || month == 1 || month == 2)
Hyx%FN= [font="Times]season = "Winter";
&.~Xl:lq [font="Times]else if(month == 3 || month == 4 || month == 5)
s4h3mypw [font="Times]season = "Spring";
UlF=,0P [font="Times]else if(month == 6 || month == 7 || month == 8)
9U$n;uA [font="Times]season = "Summer";
j{PuZ^v1 [font="Times]else if(month == 9 || month == 10 || month == 11)
o_C
j o [font="Times]season = "Autumn";
t F^|,9_< [font="Times]else
aMI\gCB/ [font="Times]season = "Bogus Month";
*ElR [font="Times]System.out.println("April is in the " + season + ".");
z'FD{xdf [font="Times]}
T"ors]eI [font="Times]}
Twi:BI`. [font="Times]//这段程序输出[font="Times]:
lW}"6@0, [font="Times]//April is in the Spring.
2O}UVp> [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
$C@v [font="Times] switch语句
1xAZ0X# [font="Times] class Switch {
*tkbC2D [font="Times]public static void main(String args[]) {
<7Igd6u [font="Times]int month = 4;
agdiJ-lyQ [font="Times]String season;
kH$)0nK [font="Times]switch (month) {
?L.c~w;l [font="Times]case 12:
XoI,m8A [font="Times]case 1:
=73""ry [font="Times]case 2:
nu|paA [font="Times]season = "Winter";
57W4E{A [font="Times]break;
mqPV
Eo [font="Times]case 3:
e}e|??'(\ [font="Times]case 4:
E07g^y"}i [font="Times]case 5:
#SWL$Vm> [font="Times]season = "Spring";
(KQAKEhD! [font="Times]break;
wbg_%h: [font="Times]case 6:
,jVj9m [font="Times]case 7:
_c|aRRW [font="Times]case 8:
O{WJi;l [font="Times]season = "Summer";
'Y`.0T[& [font="Times]break;
QI\ &D)
[font="Times]case 9:
@k.j6LKbc [font="Times]case 10:
GMD>Ih.k:9 [font="Times]case 11:
NKae~ 1b [font="Times]season = "Autumn";
dfkmIO%9X [font="Times]break;
&}sC8,Sr [font="Times]default:
r2,AZ+4FP [font="Times]season = "Bogus Month";
@mM])V [font="Times]}
erG@8CG [font="Times]System.out.println("April is in the " + season + ".");
%*4Gx +b [font="Times]}
f?xc-lX5R [font="Times]}
分支语句代码下载 9AJMm1_ L\p@1N?K [font="Times]switch语句适合于条件非常多的逻辑
uYk4qorA 请看上述语句可以混合使用,请看
下载例子